Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932905AbZDCOqz (ORCPT ); Fri, 3 Apr 2009 10:46:55 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932591AbZDCOp6 (ORCPT ); Fri, 3 Apr 2009 10:45:58 -0400 Received: from mga09.intel.com ([134.134.136.24]:46003 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1765894AbZDCOp4 (ORCPT ); Fri, 3 Apr 2009 10:45:56 -0400 Content-Type: multipart/mixed; boundary="===============1405903643==" MIME-Version: 1.0 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.39,319,1235980800"; d="scan'208";a="503328276" Message-Id: <20090403144549.794157000@intel.com> References: <20090403144332.799740000@intel.com> User-Agent: quilt/0.46-1 Date: Fri, 03 Apr 2009 16:43:34 +0200 From: markus.t.metzger@intel.com To: mingo@elte.hu, tglx@linutronix.de, hpa@zytor.com Cc: markus.t.metzger@gmail.com, roland@redhat.com, eranian@googlemail.com, oleg@redhat.com, juan.villacis@intel.com, ak@linux.jf.intel.com, linux-kernel@vger.kernel.org, Markus Metzger Subject: [patch 02/20] sched: add wait_task_context_switch() fucntion to sched.h Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3447 Lines: 114 --===============1405903643== MIME-Version: 1.0 Content-Disposition: inline; filename=tip.master.sched.task_running.patch Add a function to wait until some other task has been switched out at least once. Signed-off-by: Markus Metzger --- include/linux/sched.h | 2 2 + 0 - 0 ! kernel/sched.c | 43 43 + 0 - 0 ! 2 files changed, 45 insertions(+) Index: b/include/linux/sched.h =================================================================== --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1988,8 +1988,10 @@ extern void set_task_comm(struct task_st extern char *get_task_comm(char *to, struct task_struct *tsk); #ifdef CONFIG_SMP +extern void wait_task_context_switch(struct task_struct *p); extern unsigned long wait_task_inactive(struct task_struct *, long match_state); #else +static inline void wait_task_context_switch(struct task_struct *p) {} static inline unsigned long wait_task_inactive(struct task_struct *p, long match_state) { Index: b/kernel/sched.c =================================================================== --- a/kernel/sched.c +++ b/kernel/sched.c @@ -1933,6 +1933,49 @@ migrate_task(struct task_struct *p, int } /* + * wait_task_context_switch - wait for a thread to complete at least one + * context switch. + * + * @p must not be current. + */ +void wait_task_context_switch(struct task_struct *p) +{ + unsigned long nvcsw, nivcsw, flags; + int running; + struct rq *rq; + + nvcsw = p->nvcsw; + nivcsw = p->nivcsw; + for (;;) { + /* + * The runqueue is assigned before the actual context + * switch. We need to take the runqueue lock. + * + * We could check initially without the lock but it is + * very likely that we need to take the lock in every + * iteration. + */ + rq = task_rq_lock(p, &flags); + running = task_running(rq, p); + task_rq_unlock(rq, &flags); + + if (likely(!running)) + break; + /* + * The switch count is incremented before the actual + * context switch. We thus wait for two switches to be + * sure at least one completed. + */ + if ((p->nvcsw - nvcsw) > 1) + break; + if ((p->nivcsw - nivcsw) > 1) + break; + + cpu_relax(); + } +} + +/* * wait_task_inactive - wait for a thread to unschedule. * * If @match_state is nonzero, it's the @p->state value just checked and -- --===============1405903643== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline --------------------------------------------------------------------- Intel GmbH Dornacher Strasse 1 85622 Feldkirchen/Muenchen Germany Sitz der Gesellschaft: Feldkirchen bei Muenchen Geschaeftsfuehrer: Douglas Lusk, Peter Gleissner, Hannes Schwaderer Registergericht: Muenchen HRB 47456 Ust.-IdNr. VAT Registration No.: DE129385895 Citibank Frankfurt (BLZ 502 109 00) 600119052 This e-mail and any attachments may contain confidential material for the sole use of the intended recipient(s). Any review or distribution by others is strictly prohibited. If you are not the intended recipient, please contact the sender and delete all copies. --===============1405903643==-- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/